Revert "ipv4: keep skb->dst around in presence of IP options"

ip_options_echo() does not use anymore the skb->dst and don't
need to keep the dst around for options's sake only.
This reverts commit 34b2cef2

.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>